1. Field of the Invention
The present invention relates to a workpiece inspecting apparatus and a workpiece inspecting method for rotating a workpiece having a shape portion containing projecting portions and recess portions which are repetitively formed on the workpiece, picking up images of the shape portion of the workpiece and inspecting the workpiece on the basis of the pickup images.
2. Description of the Related Art
There is known an appearance inspecting apparatus with which images of a gear wheel as a workpiece fed by a feeding unit are picked up by a camera and the presence or absence of a defect in gear teeth of the gearwheel is detected on the basis of the pickup images (for example, see JP-A-05-231842). According to this type of appearance inspecting apparatus, an impeller (turbine wheel) used for a turbocharger of an engine for a vehicle or the like is supported by a servo motor so that it is freely rotatable, step feeding is executed on the turbine wheel by the servo motor, and the rotation of the turbo wheel is stopped at an image pickup position, thereby allowing image pickup of all the vanes of the turbine wheel by a fixedly installed camera (for example, see JP-A-2009-52917).
When images of a portion which is periodically and repetitively formed on a workpiece (for example, teeth of a gear wheel, vanes of an impeller (turbine wheel) or the like) are picked up and an appearance inspection is executed on the basis of each pickup image, it is desired to pick up respective images under the same condition (for example, pick up the images at the same position).
As compared with the technique disclosed in JP-A-05-231842, the technique disclosed in JP-A-2009-52917 has a more excellent advantage that images of many places to be inspected can be picked up by rotating the turbine wheel. However, this technique step-feeds and stops the workpiece at a predetermined rotation angle, and thus needs a mechanism and a control operation for stopping the workpiece with high precision. Furthermore, the workpiece is stopped every time an image is picked up, and thus much time is required until pickup of all imaged has been completed. Still furthermore, a processing load imposed on image processing for detecting a damage or a continuous defect on the basis of pickup images is large, and thus this also causes increase of the processing time.
Furthermore, according to the above techniques, images of a workpiece are picked up under illumination in a fixed direction or from an observation point in a fixed direction, and thus a damage or the like on the workpiece may be overlooked.